Electric control system



Jan. 21, 1941. w. GARMAN 2,229,448-

ELECTRIC common SYSTEM I Filed Nov. 24 1937 4 Sheets-Sheet 1 Invehtor:George W (Barman, b9 6 Hi S At torneg.

Jan. 21, 1941. w GARMAN 4 2,229,448

ELECTRIC CONTROL SYSTEM Filed Npv. 24, 1937 4 Sheets-Sheet 2 InventorGeorgeW. Garm an,

Hi Attorn ev.

Jan- 21, 1941. w. jq A 2,229,448

ELECTRIC CONTROLYSYSTEI Fiied'nov. 24, 19:57 4 Sheets-Sheet s Fig. 7. 9394 TO MOTOR a9'-- Fig.6. I C? SATURABLE TRANSFORMER SATURABLE 1'0 PRmE79 .TRANsFpRn ER Ge orge W. Garm an,

His Attorney;

Jan. 21, 1941. G. w.- GARMAN 2,229,448

ELECTRIC CONTROL SYSTEM George W. German.

H is Attorney.

Patented Jan. 21,1941

UNITE-D,- sT A'l Es. PATENT OFFICE Emc'rmo comaor, SYSTEM George W.Garman, Scotia, N. Y., minor to General Electric York Company, acorporation of New ApplicatlonNovemberit'l, 1937, Serial 176,2814,0laims. (Cl. 172239) My invention relates to electric control sys temsand more particularly to electric valve con-, trol systems fordynamo-electric machines.

.In many industrial operations or processes it is 5 frequently desirableto control an operation by means of an electric motor, the speed ofwhich is precisely and-accurately determinable. For example, in manyapplications it is desirable to en.- ergize a direct current moteriroman associated alternating current circuit through electric valve at adefinite predetermined speed. Heretofore many of the prior artarrangements which have been employed for this purpose have entailed theuse 'of complicated and expensive control equipment and have beensusceptible to objectionable variations in speed. Furthermore, it hasbecome desirable to provide control apparatus which is entirelyelectrical in nature and operation and" which is free of moving orvibrating-contacts. In' addition,- it is important in order to obtainprecise control to dispense with the use-of mechanical speed responsivedevices because of the inherent limitations of sucharran'gement's.

It is an object of my invention to provide a new and improved electriccontrol system. It is anothenpbje'ct of my invention to provide a newand improved electric valve control system for rlynamo-electricmachines. It is afurther object of my invention to provide a new andimproved control system for electrio valvetranslating apparatus forenergizing.

a direct current motor from an alternating current supply circuit. v

In accordance with one of theillustrated embodiments of my invention Iprovide an improved control circuit for controlling an operatingcharacteristic, such as the speed, of a direct current motor. A directcurrent motor is enerthrough electric valve translating apparatusincluding electric valves'having control members for controlling theconductivities thereof. An auxiliary dynamo electric machine or a pilotgenmotor to provide a'unidirectional voltage which varies in accordancewith the speed of the'motor. The output voltage of the pilot generatoracts in opposition to a source of reference potentiaL'and theresult'antor diflexence voltage is introduced in the excitation circuitfor'the con- '-trol members of the electric valves to control theconductivities of the electric/valves in accordance with the speed of'the motor. thereby con;

a; trolling the voltage impressed on the armature means and to maintainthe speed of the motor.

of the direct curient motor. A serially connected I capacitance andresistance are connected in series relation with the'source of referencepotential and the armature of the pilot generator to delay the rateofchange -of the resultant voltage 5 impressed on the control members ofthe electric valves and hence serve as a damping means I when' thedirect current motor speed undergoes sudden variations.v A secondcapacitance is connected in shunt relation with the resistance to permita rapid rate of change of the difference voltage impressed on thecontrol members of the electric valves for small variations in speed ofthe direct current motor. I r.

In accordance with another feature of some of 15 the illustratedembodiments of my invention, I

' provide a control system for dynamo-electric ma chines in whichadirect current pilot generator furnishes a control voltage which variesas the speed of the machine tobe controlled. The ar- 20 I mature circuitor the excitation'circuit, or both, are energized from an associatedalternating current circuit througli electric valve means having controlmeans or members for controlling the conductivities thereof. -Animpedance element 25 connected in circuit with the control membersimpresses a unidirectional potential on the control members. Variableunidirectional current is transmitted through the impedance element by agized from an alternating current supply circuit and the controlelectric valves, and in a still fur 5 erator is directly connected tothe direct current ther illustrated embodiment a damping circuit isconnected between the armature of a direct can rent motorto becontrolled and the grid'circuit of the control electric valve.. For abetterunderstanding of my invention,

reference may be had to the following description taken in connection;with the accompanying drawings, and its scopewill be pointed outin theappended claims. Fig, 1 diagrammatically illustrates an embodiment of myinvention as ap- "plied to a control system'for 'a dynamo-electricmachine of thadirctcurrent type and in which valves; Fig. 2 illustratesan embodiment of my invention employing an intermediate control electricvalve between the pilot generator and the main or'power electric valves;and Figs. 3-6

represent certain modifications thereof. Fig. 7 diagrammaticallyillustrates another embodiment of my invention as applied to a controlsystem for a direct current motor arranged for operation in bothdirections of rotation. Figs. 8 and 9 diagrammatically represent stillfurther embodiments of my invention as applied to an electric valvecircuit for controlling a direct current motor in which the electricvalves are controlled by an impedance phase shifting circuit and inwhich an anti-hunting circuit is interposed between the motor and theimpedance phase shifting circuit.

Referring now to Fig. 1 of the drawings, my invention isdiagrammatically illustrated as applied to an electric valve controlsystem for a dynamo-electric machine I of the direct current typehaving'an armature 2 and a field winding 3. The field winding 3 may beenergized from any suitable source .of direct current 4. Armature 2 of.machine I is energized from an alternating current circuit 5 through atransformer 6 and through electric valves I and 8; The transformer 6comp-rises a primary winding 9 and a secondary Winding III provided withelectrically intermediate connections II, I2 and I3. The electric valvesI and B are preferably of the type employing an ionizable medium such asa gas or a vapor and each comprises an anode, a cathode I5 and a controlmeans or member I6. One terminal of the direct current armature 2 ofmachine I is connected to the intermediate connection II of secondarywinding. III, and the other terminal thereof is connected to the commonconnection of cathodes I5 of electric valves 1 and 8.

To impress on-control members I6 of; electric valves I and 8 alternatingvoltages of predetermined phase displaced, relative to the respectiveanode voltages, I employ an excitation circuit including a transformerI'I energized from secondary winding ID of transformer 6 through asuitable phase shifting circuit I8. The transformer I1 is provided witha primary winding I9 and a secondary winding 28. The phase shiftingcircuit I8 may comprise a capacitance 2| and a variable resistance 22having terminals connected to intermediate connections I2 and I3,respectively, of secondary winding I of transformer 6. Primary windingIQ of transformer I1 is connected to the common juncture of capacitance2| and resistance 22 and intermediate connection II of secondary'windingIII. Current limiting resistances 23 may be connected in series relationwith control members I6 of electric valves I and 8.

As an agency for controlling the phase of the resultant voltagesimpressed on control members I of electric valves I and 8 in accordancewith a predetermined controlling influence derived from thedynamo-electric machine I, I employ a voltage source variable inaccordance with the condition to be controlled such as an auxiliarydynamo-electric machine 24 which may be termed a pilot generator. Thepilot generator 24 may be of the direct current type having an armaturemember 25 and a field winding 26 which may be energized from anysuitable source of direct current, and which is shown as being connectedto the direct current circuit 4. I.

.cannot flow betweenanode and cathode.

provide a voltage divider- 21, comprising 'a resistance 28 and anadjustable contact 29, for

producing a variable or adjustable source of reference potential againstwhich the output voltage of the pilot generator 24 acts. The voltagedivider 21 may be energized'from any suitable source of unidirectionalvoltage 33. It will be noted that the voltage of the voltage divider 21and the voltage of the pilot generator 24 act in opposition to introducein. the excitation circuit for electric valves 1 and 3 a resultantunidirectional voltage which varies, in accordance with the speed of thedynamo-electric machine I.

In order to control the rate of change of the difference voltageprovided by pilot generator 24 and voltage divider 21 and hence tocontrol the rate of change of potential of control members I6, I providea serially connected capacitance 3| and a resistance 32 whichare.connected in series relation with the voltage divider 21 andarmature 25 of pilot generator 24. Capacitance 3| and resistance 32serve as a damping means for great variations in speed ofthe machine I.In order to provide a means for permitting precise and accurate controlof the speed of machine I in accordance with small variations in speedthereof, I provide a capacitance 33 which is connected in parallelrelation with resistance 32. This capacitance permits a'rapid rate ofchange of the potential of control members I6 for small changesinspeedof the dynamo-electric machine I.

The operation of the embodiment of my invention shown in Fig. 1 will beexplained by considering the system when dynamo-electric machine I isoperating as a direct current motor. A unidirectional current will betransmitted to the armature 2 of machine I through electric valves 1 and8 which operate as a rectifier en-' ergized from the alternating currentcircuit 5.

The manner in which the electric valves I and 8 control the voltageimpressed on armature 2 of machine I will be well understood by thoseskilled in the art. For a given positive anode voltage there is acertain value of grid voltage which is termed the critical grid-voltage.'When the grid is more negative than this value, current If the grid ismore positive than this critical value,

current can flow and the magnitude of the current will be determinedprincipally by the external resistance of the associated circuit. Oncethis current is established between anode and cathode, in the.usualcommercial arrangement the grid can exert no further control unless theanode voltage is reduced to avalue near zero.

'When the anode voltage becomes zero, the curimpressed on controlmembers I6 by transformer II lag the respective anode. voltages bysubstantially 90 degrees. Voltage divider 21 is adjusted so that thevoltage which this element introduced into the excitation circuit issomewhat greater than the negative unidirectional biasin potentialprovided by pilot generator 24. By the proper adjustment of thevoltagedivider, the

' impressed on' armature 2 of machine I.

predetermined range to be maintained, the voltage produced by the pilotgenerator 24 will correspondingly decrease to eflect an increase thepositive resultant unidirectional voltage im-' pressed on controlmembers I6 of electric valves I and 8,1thereby effecting a virtualadvancement in'phaseiof the resultant voltages impress ed on controlmembers I6 and there increasing the output voltage of the electricvalves 1 and 8 virtue of this increase in voltage, the speed of.

the machine I will-be increased tending to reor the contr lmembervoltages. .Because of this retardation phase of the voltages impressedon control niembers I6, the speed oimachine I will'be decreased,therebyrestoring. the speed oi machine I to the predetermined range ofoperation. l s

Capacitance and resistance 32 serve as a. damping means to prevent thespeed of the mav chine I from over-shooting the predetermined range ofspeed values to be maintained. The damping eilect of the capacitance 3|and resistance 32 for large or substantial changes in speed of machine Iis dueto the fact that the charge on the capacitance 3| cannot changeinstantaneously relative to variations in potentials across itsterminals' The capacitance 33,-which is connected in shunt relation with"resistance 32, permits small variations in voltage to be transmitted tocontrol members I6 of electricvalves I and 8 and to controlthese'electric valves within narrowly defined ranges oi operation.Capacitance 3| and resistance 32, acting in conjunctionwith capacitance33, serve to control the conductivities of electric valves I and 3 .toeflect stable operation when the speed of machine I is held withinnarrowly defined limits; capacitance 3| and resistance 32 preventover-shooting oifthe limit to be maintained, and capacitance 33 acinvention for controlling a dynamo-electric machine or the directcurrent type. The arrangement of Fig. 2 is similar in many respects tothat of Fig. 1 and corresponding elements have been assigned likereference numerals. Armature 2 of machine I may be energized from anysuitable source 01 direct current 34, and field winding 3 of machine Imay be connected to the armature circuit of machine ,I through a currentcontrolling device such as an adjustable resistance 35; Electric valvesI and 8 may be energized from the alternating current circuit 5 througha transformer 36 having a primary winding 31 and a secondary winding 38.Thetransformer 7o- 36 may also be provided with asecondary winding 36for energizing cathode heating elements. for electric valves 1 and 3. v

, e Asource of alternating current of 'predeter be obtained by utilizinga secondary winding 40 of transformer 36 whichener'gizes any suitablephase shiiting circuit 4|. The phase shifting circuit 4| may be oi thestatic type, and may include a capacitance 42 and a resistance 43, whichenergizes a transformer 44 having a primary winding 45 and a secondarywinding 46 provided with an'el trical intermediate connection 41.Terminals oi the secondary winding 46 are connected to control membersl6'of' electric valves I and 8 through current limiting resistv ances23. Capacitances 48 and 49 may becon nected across control members f|6and cathodes transient voltages which mayexist inithe control circuits.

As'an agency for impressing on control mem bers I6 oi electricvalves Iand 8 a potential which varies in accordance with a'predeterminedinfluence derived from machine I, I provide a suitable impedance elementsuch as a resistance 50 which is connected betweencathodes I5 of valves1 and 8 and the electrical intermediate- I connection. 41 of transformerwinding" 46. To transmit variable unidirectional currents throughresistance 50 in accordance with the controlling influence, such as thespeed of machine I, I

. provide an electronic discharge device 5|, which i is preferably ofthe high vacuum type, having an anode 52, a cathode 53 and acontroLmeans such as a. grid 54. The voltage 01' the pilot gen-- erator24, which varies as the speed of machine I,

is impressed on grid 54 of electronic discharge device 5| througharconductor 55. A suitable source of unidirectional voltage 56 and avoltage divider 51 are connectedto produce a source of l5 or electricvalves I and 8 to absorb extraneous reference potential which acts inopposition to.

the voltage provided by armature 25 of pilot generator 24 so that theresultant voltage impressed on grid 54 varies as adifieren'ce voltage.While I have chosen to show the sourc of ref-'- erence potential ascomprising a voltage divider and a direct current source, it is to beunderstood that I may employ any oher suitable arrangement known in theart. .As a source of energization' for electric discharge device 5|, Iemploy a transformer 58 having a primary winding 59 and secondarywindings 6li=and 6|. Secondary winding 6| is connected to cathode 53 ofdis charge device 5| to eifect energization'thereoi', and secondarywinding 60 is connected to a rectifier 63 and an electrical wave filter63 to impress a unidirectional voltage across anode 52 and cathode 53.The rectifier 62 may be of the full wave type and may employ elements ofthe dry surface contact type such as that disclosed and claimed inUnited States Letters Patent No. 1,640,335, granted August 23, 1927,uponan ap plication \of Lars O. Grondahl. The electrical wave filter 63'may comprise an inductance 64, a capacitance 65 and a resistance 66.,Cathode 53 of electronic discharge device 5| is connected to the lowerterminal of resistance 50 through a. conductor 61, and the upperterminal of re- 1 sistance 50 is connected to the negative terminalofthe wave filter 63 through a-conductor 68.,

As an agency for controlling the rate of change of the voltage impressedon grid 54 oiTelectronic 1 discharge device 5| in accordance with thevoltage appearing across the terminals of resistance. 50, I provide .adamping circuit including a serially connected capacitance 69 and aresistance 10 which areconnected to the grid c rcuitfor device 5|. Thisdamping circuit is connected to prevent hunting of the control systemand aflords an ar- 'rangement for obtaining precise control of machine Iduring variable load conditions.

The operation of the embodiment of my invention shown in Fig. 2 will beexplained by considering the machine I when it is operating as a di rectcurrent motor. Armature 2 of machine I is energized from circuit 34, andfield winding ,3 of machine I is energized primarily through electricvalves 1 and 8 which control the speed of machine I. As will be wellunderstood by those skilled in the art, the average current conductedode voltages the average current of these electric valves issubstantially zero when the electric valves are energizing an inductivecircuit. Phase shifting circuit 4I impresses on control members I8 ofelectric valves I and 8, through transformer 44, control voltageslagging by 90 electrical de-' grees the respective anode voltages. Thesystem 'is arranged so that the positive unidirectional controlpotential impressed on control members I6 by resistance is of suflicientvalue to cause electric valves I and 8 to transmit the requisite amountof current to maintain the speed or machine I at the desired value.Electronic discharge device 5| controls the amount of unidirectionalcurrent transmitted to resistance 50, thereby controlling the magnitudeof the unidirectional con trol voltage appearing across its terminalsand controlling the conductivities of electric valves I and 8 inaccordance with the speed of machine I.

Resistance 51 is adjusted so that the resultant voltage impressed ongrid 54 of electronic discharge device 5| maintain the speed of machineI at the predetermined value under steady load conditions. I

If it be assumed that the speed. of machine I increases to a' valueabove the predetermined value or range to be maintained, the potentialimpressed on grid 54 of discharge device 5| will become more positiverelative to the potential of the cathode 53 to cause the device 5I tosupply a larger amount of current to resistance 55, thereby increasingthe positive unidirectional potential impressed on control members I6ofelectric valves I and .8. This increase in positive potential willeffect/5 virtual advancement inphase of the resultant voltages impressed"on control members I6, causing the electric valves I and 8'to conduct agreater value of, average current and thereby increasing theenergization of the field winding 3 of machine I. 'This increase inenergization of field winding 3 will effect a reduction in speed of themachine I-tending to restore the machine to the predetermined valueorrange of speed to be maintained. t

The manner in which the damping circuit including capacitance 69 andresistance In controls .the rate of change of the potential of grid 54to prevent hunting may be described as follows. Under the above assumedconditions, as the conductivity of the discharge device 5I is increased,due to the more positive voltage being impressed on grid 54, theincident increase in voltage appearing across the terminals ofresistance 50 is reflected by the flow of current through resistanceattains that value which will III and capacitance 59, temporarilyraising in a positive direction the potential of the cathode 53 relativeto the potential of grid 54. This rise in potential is, of. course,occasioned by the charging current of capacitance 69 and introducesaexplained the operation of the arrangement shown in Fig. 2 forincreases in speed of machine I above a certain value, it is to beunderstood, of

cours'e,that the arrangement functions in a .sim-- ilar manner fordecreases in speed of the machine I, tending to restore the speed of themachine to the desired value.

Fig. 3 represents another embodiment of my invention similar in manyrespects to that shown in Fig. 2, and corresponding elements have beenassigned like reference numerals. A bridge circuit II may be connectedbetween the armature 25 of pilot generator 24 and the grid 54 ofelectronic discharge device 5I to accentuate the voltage variationsoccasioned by variations .in speed of the machine I. The bridge circuitII may comprise impedance elements such as resistances I2 having linearimpedance-current characteristics and may also include impedanceelements such as resistances 13 having nonlinear impedance-currentcharacteristics. Resistances I3 may be made of the material disclosedand claimed in- United States Letters Patent No. 1,822,742, grantedSeptember 8, 1931, upon an application of Karl E. McEachron and assignedto the assign-ee of, the present application. 1

The operation of the arrangement shown in Fig. 3 is; substantially thesame as that explained in connection with the embodiment shown in Fig.2. The bridge circuit II accentuates the voltage variations of armature25 of pilot generator 24 and provides a suitable arrangement forcontrolling the conductivity of electronic discharge device 5| which inturn controls the unidirectional voltage impressed on control membersII; of electric valves I and 8. I In Fig. 4 there is diagrammaticallyrepresented a still further embodiment of my invention showing severalelements included in the arrangement of Fig. 2, and these elements havebeen assigned corresponding reference numerals. The damp- A suitableimpedance element suchas a resist- I ance 14' may be connected in seriesrelation with the armature 2 of machine I to produce a voltage whichvaries in accordance'with the armature current. This voltage .isintroduced into the circuit for grid 54 of discharge device 5I and actsto prevent hunting.

The operation of the embodiment of my invention shown in Fig. 4 issubstantially the same as that explained above in connection with Fig.2. During transient conditions the voltage appearing across theterminals of resistance I4 causes a charging current to flow through acircuit including capacitance 68 and resistance III, establishing acrossthe terminals of resistance III a voltage to modify the potentialdifference betweengrid 54 and cathode 53 thereby preventing hunting ofmachine I.

Fig. 5 shows another embodiment of, my invention inywhich an alternatingcurrent pilot generator I5 is employed to generate an alternatingvoltage, the frequency of which varies in accordance with the speed ofthe machine I. The pilot generator 15 is provided with a field windingI8 and an armature circuit I1. In order to provide a suitablearrangement for producing an alternating voltage of peaked wave form, Iprovide a saturable transformer I8 having a secondary winding "I9. Arectifier is connected across the terminals of secondary winding 19 toproduce a unidirectional voltage the magnitude of which varies with thespeed of the machine I. The output terminals 8I of rectifier 80 may beconnected to cathode 53 and grid 54 of electronic discharge device 5Ishown in Fig. 2.

The arrangement of Fig. 5 also operates to control the speed of machineI under varying load conditions. The unidirectional voltage appearingacross the terminals 8I of rectifier 80 varies in magnitude inaccordance with the frequency of the voltage impressed on transformerI8; therefore, the conductivity of the electronic discharge device 5|,shown in Fig. 5, is controlled in accordance with the speed of machine Ito effect the, desired regulating action.

In Fig. 6 there is shown a modification of the embodiment of myinvention shown in Fig. 5 as applied to an arrangement for controllingthe energy input to a prime mover 82 which drives a generator, such asan alternating currentgenerator 83 having a field winding 84 and anarmature circuit 85. The input to prime mover 82 may be controlled by asuitable valve controlling motor 88 having an armature member 81 and afield winding 88. Output terminals M of rectifier 80 may be connected tocathode 53 and grid 54 of an electronic discharge device 5|, shown inFig. and thearmature and the field winding 88 of the valve motor 86 maybe energized from an arrangement similar to that shown in Fig. 2.

In operation the arrangement shown in Fig. 6 performs substantially thesame as that explained in connection with Figs. 2 and 5. The

' frequency of the alternating voltage generated by pilot generator I5varies in accordance with the speed ofthe generator 83, and theenergization v of the valve motor 86 is controlled to maintain the speedand the frequency of the generator 83 at a predetermined value or rangeof values.

In Fig. 7 of the accompanying drawings there is shown another embodimentof my invention as applied to a, control system for operating areversible direct current motor. A direct current motor 89 having fieldwinding and armature members SI and 92 is arranged for operation ineither direction of rotation. The field winding 90 may be energized fromany suitable source of direct current 93 through a current controllingresistance 94. To selectively energize armature members 9I and 92, Iprovide a pair of electric valve translating apparatus and 96 which areassociated with armature members 9| and 92,-

respectively. The electric valve translating apparatus 95 and 98 arearranged. to transmit unidirectional current to armature members 9| and92 and the armature members 9| and 92 are arranged to rotate motor 89 inopposite directions. The translating apparatus 95 and 98 may beenergized from any suitable source of alternating current 91 and includeelectric valves 98, 99 and I00, II", respectively. These-electric valvesare preferably of the type employing an ionizable medium and eachincludes an anode I02, ,a cathode I03 anda control member I04.

To impress on the control members I04 alter-- nating voltages ofpredetermined phase displace- 91 to supply current to heating elementsof cath-.

ment relative to the respective anode voltages, I employ a phaseshifting circuit I05 which may be any of the forms known in the art. Thephase shifting circuit I05 comprises a capacitance I06 and ,a-resistanceI07 and impresses alternating voltages on control members I04 which havea lagging phase displacement of substantially 90 electrical degreesrelative to the respective anode voltages. A transformer I08 having aprimary winding I09 and secondary windings H0 and III v is connectedbetween the phase shifting circuit I05 [and control members 'I04 ofelectric valves 98-IOI. Secondary-windings H0 and III are provided withelectrical intermediate connections A transformer H3 is connected tocircuit odes I03 of electric valves 98-IOI.

As an agency for controlling selectively the conductivities of electricvalves 98, 99 and I00,

1 IN to effect control of the speed and the direction of rotation ofmotor 89, I provide resistances H4 and H5 which are'associated withelectric valves 98, 99 and I00, IOI, respectively. The resistances H4and H5 have a common juncture I I6 and the terminals of the resistancesare connected to the electrically intermediate connections II2 ofsecondary windings H0 and II I of transformer I 08. To control thecurrent transmitted through resistances H4 and H5 in accordance with thespeed and the direction of rotation of motor 89, I provide a pair ofelectronic discharge devices I I1 and H8 which .are preferably of the.high vacuum type and each comprises an anode II9, a cathode I20 and agrid I2I. The electronic discharge devices III and H8 'transmit variableunidirectional currents through resistances H4 and IIS to impressvariable unidirectional control potentials on control members I04 ofelectric valves 98-IOI, inclusive.

To supply unidirectional current to electronic discharge devices In andH8, and to supply a positive unidirectional biasing potential forcontrol members I04 of electric valves 98-IOI, I employ circuits I22 andI23 respectively, each of which comprises a rectifier I24 and anelectrical .wave filter I25 including an inductance I26, a capacitanceI21 and a resistance-I28. The rectifiers I24 may be of the full wavetype and may include elements of the dry surface contact type.

,A transformer I29 may be connected between circuits I22 and I23 and asuitable source of .alternating current such as circuit 91. TransformerI29 is provided with secondary windings I30, I3I and I32. The secondarywinding I32 is provided with an electrical intermediate connection I33.

Secondary windings I30 and I 3I energize rectifiers I24 of circuits I22and I23, respectively.

{Secondary winding I32 energizes the heating elements for cathodes I20of electronic discharge devices In and H8.

A pilot generator I34, having an armature member I35 and a field windingI36, is provided as an agency for producing a voltage which varies asthe speed and the direction of rotation of motor 89 and may bemeclfanically coupled thereto. The pilot generator I34 may be of thedirect current type. A bridge circuit I31 is connected to the armatureterminals of the pilot generator I34 and may comprise linear resistancesI38 and nonlinear resistances I39. The nonlinear resistances may be ofthe type described and claimed in the above mentioned patent of Karl B.

McEachron.

A pair of damping circuits are connected between the field circuit ofmotor 89 and the grid and'comprises a capacitance l 42 circuits forelectronic .discharge devices II 1 and H8. One of these circuitsisassociated with electronic discharge device I" and comprises acapacitance I40.-;and a resistance I41, and the other is associated withdischarge device I I8 I43. Resistances I4I"'and I431ar'fconnected to thebridge circuit I31 and a commonjuncture I44 of these resistances isconnected to the cathodes I20 of discharge devices H1 and H8 through aconductor I45 and through secondary winding I32 of transformer I29.

The operation of the embodiment/of my invention shown in Fig. 7 will beexplained by con sidering the arrangement when the machine 80 isoperating as a direct current motor and when the system is arranged toefl'ect control .of the speed of machine 89 for either. direction oirotation. If it be assumed that armature member 90 of motor 89 rotatesin a clockwise direction when armature member 9| predominates, the

control of the motor 89 is eifected predominately by electric valves 88and 99 which in turn are controlled by the electronic discharge deviceI". For this direction of rotation, the pilot generator will produce aunidirectional voltage of a predetermined polarity such that the voltageimpressed on grid I2I of discharge device II! 'is positive. Dischargedevice I" will conduct variable undirectional currents throughresistance 4, in accordance with speed variations of motor 89, toimpress variable positive unidirectional potentials on control membersI04 of.electric valves 98 and 99. Circuit I22 impresses unidirectionalvoltages across the anodes and cathodes of electronic discharge devicesII1 and H8 through 'rnerei'ore, theresultant potentials impressed oncontrol members I04 of electric valves 88-IOI is the algebraic sum ofthe lagging quadrature component due circuit i05, the voltage producedby rectifier I24 of circuit I23 and the voltages arr-- pearing acrossthe terminals of resistances H4 and H5.v

If it be assumed that the speed of the motor 89 increases to a valueabove the value to be maintained, the output voltage .of the pilotgenerator 1'34 will increase correspondingly'and the voltage impressedongrid I2I '1 discharge de vice II! will increase .in a positivedirection, effecting an increase in the unidirectional ourrenttransmitted through resistance 444. This increase in current occasions adecrease in the resultant positive unidirectional .voltage 1mpressed oncontrol members I04 of electric valves 98 and 99'and ultimately effectsa decrease in thevoltage impressed on armature 8I; By virtue of thisdecrease in armature voltage, the speed or the motor 89 will be restoredto the desired value; 0n the other hand, :it the speed decreases thesystem will. respond inva similar'mannerto .efi'ect an increase in thevoltage impressed on armature winding 8i, tending to'restore the motorspeed. to the desired VBJUBar For counterclockwise rotation, thearmature winding 92 predominates and the current .for

this winding is supplied'by electric "values "if.

Q a resistance and -IOI which in turn are controlled by electronicdischarge device H8. The operation for comaterclockwise rotationis'substantially the same as that explained above for clockwiserotation.

The damping circuits including, capacitances I40 and I42 and resistancesHI and I42 operate to introduce compensating voltages in the gridcircuits for electronic discharge devices II! and H8 in accordance withthe field voltage of motor 89. Sudden changes of field voltage causeourrents to flow through resistances HI and I43 which are the chargingcurrents for capacitances M0 and I42, respectively. The polarities ofthe voltages appearing across the terminals of resistances MI and I42under the transient conditions will tend to modify or compensate for thevoltage variations impressed on grids I2I by pilot generator I'34,thereby preventing hunting of the motor 88.

. In Fig. 8 of the accompanying drawings, there is illustrated anotherembodiment or'my invention as applied to an electric valve system {orcontrolling. the speed of a direct current motor.

Many of the elements of the arrangement shown.

in Fig. 8 are similar to those shown in Fig. 1 and correspondingelements have been assigned like reference numerals. A smoothinginductive reactance I48 is connected in series relation with thearmature 2 of the direct current motor I and capacitances I41 and I48are connected across control members I6 and cathodes I 5 of electricvalves 1 and 8 to absorb extraneous transient voltages.

In order to control the conductivities of the electric valves I and 8 inaccordance with an operating condition or electrical characteristic ofthe direct current motor I, I provide a phase shifting circuit I49 whichcontrols the phase of the periodic voltages impressed on control memhersI 5. The impedance phase hitting circuit I49 includes a resistance -I50and a saturable inductive device I5I having a control'winding 452. Thecontrol winding I52 is energized in accordance with the difierencevoltage provided by the voltage divider 2'! and the output voltage ofthe. pilot generator 24. The potentiometer 21. is adjusted so that thevoltage supplied thereby is greaterthan that produced by the-pilot geneerator 24. I

As" an agency for controlling the energization of the control windingI52 of the saturable inductivedevice =I5I in accordance with the rate ofchange of voltage applied to the armature member 2 of motor 4, .Iprovide an anti-hunting means comprising a serially connectedcapaci-tance I52, and a resistance-564. Aunidirectional conductingdevice 456 is connected in series with control winding 45-2. Thecapacitance I53, resistance 454 and armature (IflPilOt generator 24--are connected inseries ems armature 2. :The voltage appearing across theterminals of the resistance I54 is "in a direction tions inspeed of thedirect current-motor I.

. .A voltage divider I68 zinc'luding-a resistance-I51 and as-contrcdlingmember 158 may :he canceled in series relation with the edirect-oummisomxze '4 and the field winding 3-biiiheldtrect current motor -I andserves'as a means 101' imntrolling themergizationtlmraoi.

The operation of the arrangement :01! any invention shown in Fig.8he-mmhined by'nconsidering the system when mm 2 :of mot-1r 1 isenergized :fnom them: martending to oppose tzhht introduced :in thecircuit .by the pilot generator il-and cecasiimed hymn- Of course, theelectric valves 1 and 8 conduct current alternately to supplyunidirectionalcurrent to armature member 2. Alternating voltagesvariable in phase are impressed-oncontrol members I8 of electric valves1 and 8 to control the conductivities thereof in accordance with thespeed of the motor I tending to maintain the speed at a predeterminedconstant value. The output voltage of the pilot generator 24 varies inaccordance with the speed of the direct curv rent motor I and hencevariably energizes the control winding I52 of the saturable reactor IIin accordance with the variations in speed tending to maintain the speedconstant. The mem ber 29 of the voltage'divider 21 is adjusted so thatthe output voltage thereof is greater than the output voltage of thepilot generator 24. The control winding I52 is energized through acircuit including the lower portion 'of resistance 28 of the voltagedivider 21, resistance I54, the uni directional'conducting device I55and armature "1:25 of pilot generator 24. It will be noted that thevoltage produced by the pilot generator 24 minal.

is in opposition to that produced by the voltage divider 21.

If it be assumed that the speed of the direct current motor I decreasesto a value below the predetermined value to be maintained, the voltageproduced by the pilot generator 24 will decrease, effecting thereby anincrease in the resultant unidirectional voltage acting in the circuitwhich energizes the control winding I52 of the saturable reactance I5I.As a result thereof, the current supplied to the control winding I 52 isincreased, effecting an advance in phase of the alternating voltagesimpressed on the control members I8 of electric valves 1 and 8 andcausing the electric valves to impress on armature member 2 of thedirect current motor I an increased unidirectional voltage tending to'restore the motor speed to the predetermined value. The anti-huntingcircuit including the capacitance I53 and resistance I54 will respond tointroduce in the circuit a compensatory effecttending to prevent theovershooting of the controlling action. For example, when the electricvalves 1 and 8 increase the voltage applied to the armature member 2,the lower terminal of the armature 2 will be raised to a value morepositive than the fir rent will flow through the capacitance I 53,armature 25 of pilot generator 24. and resistance I 54.

This current will be in a direction such that at a potential positiverelative to the upper ter- The voltage of the resistance I54 is in adirection tending to oppose that occasioned by the change in speed ofthe motor I. In other words, the voltage across the capacitance I54tends to decrease the increment of current transmitted to the controlwinding I52 under the conditions above described. In this manner ananti-hunting action is introduced to prevent overshooting of thecontrolling action. The unidirectionalv conducting 'device' I55 insuresthat only unidirectional current is supplied'to the control winding I52.

Fig. 9 illustrates another embodiment of my invention as applied to anelectric valve system for variably energizing the excitation or fieldcircuit of the direct current motor to control the speed thereof. issimilar in many respects to that of Fig. 8 and viously prevailing valueand a cur- The arrangement of Fig. 9'

corresponding elements have been assigned likeconducting device I59, aresistance I60 and a I capacitance I6I which are connected across theterminals of the excitation or field winding 3 of the motor I. deviceI59, resistance lfill and capacitance I6l may be connected in seriesrelation with a resistance I62 so that the complete circuit is connectedacross the field or excitation winding of machine I. A parallelconnected capacitance I63 and resistance I64 are connected between thelower terminal of resistance I62 and the positive terminal of thedirectcurrent motor I to introduce in the control circuit a voltagewhich varies in accordance with the rate of change of the voltageapplied to the terminals of field winding 3;

The embodiment of my invention shown in Fig. 9 operates in substantiallythe same manner as that explained above in connection with Fig. 8. Thefield winding 3 of the direct current motor I is variably energized fromthe alternating current circuit 5 through electric valves 1 and 8 inaccordance with the speed of the direct current motor I. The alternatingvoltages impressed on control members I6 are varied in phase to controlthe conductivities 'of the electric valves 1 and 8. Control winding ;I52of the satu'rable in ductive reactance I 5I is variably energized inaccordance with the dirference in voltages produced by the pilotgenerator 24 and the voltage divider 21. The control winding I52 isenergized through a circuit including armature 25 of pilot v generator24, the unidirectional conducting device I59, resistance I80 and theupper portion of the resistance 28 of the voltage divider 21.

If it beassumed. that the speed of the direct current motor I increasesto a' value above the predetermined value to-be maintained, theresultant unidirectional voltage impressed on the control winding I52 isincreased due to the increase in voltage of the pilot generator 24.Coincidentally therewith; the unidirectional current supplied to thecontrol winding I52 is increased to effect-an advancement in phase ofthe alternating voltages impressed on the control members I5 of theelectric valves 1 and 8 relative to theapplied anode-cathode voltages,so that these valves increase the average current transmitted to fieldwinding 3 of direct current motor I", thereby tending to reduce thespeed to the predetermined value. The circuit including theunidirectional conducting device I59, resistance I60, capacitance I6Iand the resistance I 82 functions to introduce an anti-hunting effectinto the circuit for control winding I52 in the following manner. Underthe conditions stated, when the electric valves 1 and 8 increase thevoltage applied to the field winding 3 of motor I, a charging currentwill flow through the circuit including :the unidirectional conductingdevice I59, resistterminal, and this voltageis in a directionopposite'to the increase in voltage of the pilot generator 24 occasionedby the increase in speed.

Theunidirectional conducting the action of the regulating system byintroducing t in the circuit for these elements a voltage which tends tolimit the antihunting-action.

While I have shown and described my invention as applied to particularsystems 01' connecfrom said source and comprising an electricvalvetions' and as embodying various devices diagrammatically shown, itwill be obvious to those skilled in the art that changes andmodifications may be made without departing from my invention, and I,therefore, aim in the appended claims to cover all' such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to obtain by Letters Patent of the UnitedStates is:

1. Incombinatlon, a source of current, ,a dynamo-electric machine of thedirect current type having an armature winding, electric translating.

apparatus connected between said .source and said armature winding andincluding electric valve meanshaving a control means for control:-

ling the conductivity thereof, an auxiliary direct I current machine forproducing a unidirectional voltage which varies in accordance with acontrolling influence derived from'said first mentioned machine, a'source of unidirectional voltage which opposes the first mentionedvoltage, and antihunting'means cpnnected in series relation with saidcontrol means, said auxiliary machine and said last mentioned source andresponsive to the difference between the first mentioned and the secondmentioned unidirectional voltages-for controlling the rate of change ofthe' voltage impressed on said control means.

2. In combination, a source 0! current, a dynamo-electric machine ofthedirect current type having an armature winding, electric translatingapparatus connected between-said source and said armature winding andincluding electric valve means having a control means for controllingthe conductivity thereof, an auxiliary direct current machine forproducing a, unidirectional voltage which varies in accordance with acontrolling influence derived from said first men' tioned machineyasource'of unidirectional voltage which opposes the 'firsjt'mentionedvoltage, damping meansresponsive to the difference between theilrstmen'tloned and the secondmentioned unidirectional voltages andbeing connected in series relation with said control means,

said auxiliary machine and'said'source and comprising a serioonneeted'capacitance and .a resistance for slaying a change in thecontrol -means potential, and'a capacitance connected in parallel withsaid resistance;

3. In combination, a dynamo-electric machine comprising excitation andarmature circuits, a

source or alternating current, means energized having a. control memberfor controlling the energization of said excitation circuit, a circuitfor energizing said oontrpl'member and comprising a resistance, meansfor transmitting current through said resistance comprising arr-electricdischarge device having a grid for controlling the potential of thecontrol member 01' said valve,

a. pilot generator of the direct current type for impressing onsaid grida potential which varies as .a predetennined controlling influencederived".

from said machine, and a damping circuit comprising a capacitanceconnected in series relation with a resistance for delaying a change inthe ternating current, electric translating apparatus connected betweensaid source and said excitation and armature circuits for transmittingunidirectional clnrent theretoand comprising an electric valve having acontrol member for controlling the conductivity thereof, a. circuit forenergizing said control member-and comprising a resistance, meanscomprising an electric discharge device having a grid for controllingthe potential of said control member by transmitting variableunidirectional currents through said resistance, a pilot generator 01the direct current type mechanically coupled to said ma. chine torimpressing on said grid a potential which varies as the speed of saidmachine, and a damping circuit comprising a.capacitance con- I nected inseries relation with a resistance for delaying a change in the gridpotential of said discharge device occasioned directly by variations inthe voltage of said pilot generator.

I GEORGE w; GARMAN.

variations in the voltage of

